This invention relates in general to evaporation and distillation apparatus of the wobbling-type described in U.S. Pat. Nos. 4,230,529 and 4,441,963, and to the improved evaporator using a whip rod in each heat transfer tube as described in applicant's parent application U.S. Ser. No. 598,473 (U.S. Pat. No. 4,618,399). More specifically, it relates to an orbital drive and suspension system and liquid feed arrangements compatible with this drive system.
The wobbling type of evaporator, as discussed in the aforementioned U.S. patents, has the advantages of a high heat transfer coefficient and a low power requirements for operation. However, in many chemical engineering applications, capital and maintenance cost of the equipment are crucial to the user. The cranks, bearings, and complicated seals employed inside the evaporator as described in applicant's earlier U.S. Pat. No. 4,441,963 has been found to be impractical in the chemical industry where most of the working medium are either corrosive or sensitive to contamination.
In addition, it has been found to be difficult and costly to manufacture and assemble the drive arrangements disclosed in these U.S. patents. They all involve a common drive shaft, bearings and eccentrics to develop the characteristic wobbling motion of the tube or tubes with respect to a support structure for the tubes. To have a good dynamic balance during operation, these drive parts must be machined to close tolerances, with attendant increases in cost. Assembly is also critical, and more costly, since there are a large number of components which must be assembled in a precisely defined manner in order to avoid misalignments that will produce a dynamic imbalance. Wear of the moving components also can introduce a deterioration in the balance of the wobbling tubes and the performance of the evaporator.
The present invention overcomes these problems by simplifying the construction, and thereby increasing the reliability, while reducing the capital cost. Specifically, a novel orbital drive and suspension system replaces the positive displacement drive, such as cranks or eccentrics, which were used previously to generate the wobbling motion.
It is therefore a principal object of this invention to provide a wobbling tube type evaporator that provides a good dynamic balance free from residual vibratory forces and moments.
Another object is to provide an evaporator with the foregoing advantages that also has a simplified construction, and a reduced cost of manufacture.
Yet another object is to provide an evaporator with the foregoing advantages that is reliable and offers low maintenance costs.
Another object is to provide an evaporator with the foregoing advantage which avoids any positive eccentric-mechanical drive and in certain embodiments is automatically self balancing with changes in the mass of the evaporator and fluids being processed.
Yet another object is to provide an evaporator with an improved fluid distribution that reduces entrainment, has a low cost of manufacture, and is compatible with the drive system of the present invention.
Still another object is to provide an evaporator with the foregoing advantages that adapts for operation with a whip rod fluid distributor mounted from either above or below the wobble tube or tubes.